208 TEANSACTI0X3 AND PROCEEDINGS OF THE [Sess. l^tti. 



quantity of carbonic anhydride excreted. If this variation 

 exists, it was overshadowed bj the effect of unavoidable 

 differences in the samples of barley, or by some other un- 

 known cause. The main fact remains, that all the experi- 

 ments show a slight increase of germi native respiration in 

 the samples of barley grown in obscurity. 



In the second series of experiments (in which the 

 carbonic anhydride was measured volumetricallyj the seeds 

 were placed in a large tube with about 120 c.c. of air, and 

 potassa solution was present in the tube, to absorb the 

 carbonic anhydride as it was produced. The average 

 i^uantity of carbonic anhydride produced in twenty-four 

 hours throughout the experiments would be about 6 C.C. 

 (varying from 4 to 8 c.CJ, which would give 0'2o c.c. 

 per hour, and there can be no doubt that the greater part 

 of this quantity would be absorbed by the potassa solution 

 in the same time, i.e. one hour. It is evident, therefore, 

 that the contamination of the air by the presence of un- 

 absorbed carbonic anhydride must be very slight indeed, 

 and far below that which obtained in the first series of 

 experiments, and also that the disturbing effect of such 

 contamination on the results would be absent in the second 

 series. 



In order to test this theory, I performed a few addi- 

 tional experiments with the same apparatus used in the 

 second series, but instead of absorbing the carbonic anhy- 

 dride as it was formed, I allowed it to remain in contact 

 with the seeds. At the end of each experiment, a portion 

 of the air was withdrawn from each tube, and a measured 

 quantity analysed, to determine the quantity of carbonic 

 anhydride produced in each tube. The following are the 

 results obtained in this wav : — 



